Additively manufactured interlocking casting core structure with ceramic shell

ABSTRACT

The present disclosure relates to a method of forming a cast component and a method of forming a casting mold. The method is performed by connecting at least one wax gate component to a ceramic core-shell mold. The ceramic core-shell mold includes at least a first core portion, a first shell portion, and a second shell portion, wherein the first shell portion is adapted to interface with at least the second shell portion to form at least one first cavity between the core portion and the first and second shell portions. The core-shell mold may be inspected and assembled prior to connection of the wax gate component. At least a portion of the ceramic core-shell mold and the wax gate component is coated with a second ceramic material. The wax gate component is then removed to form a second cavity in fluid communication with the first cavity.

INTRODUCTION

The disclosure generally relates to investment casting core-shell moldcomponents and processes utilizing these components. The core-shell moldmade in accordance with the present invention includes integratedceramic filaments between the core and shell of the mold that can beutilized to form passages and/or holes in the cast component made fromthese molds. The integrated core-shell molds provide useful propertiesin casting operations, such as in the casting of superalloys used tomake turbine blades and stator vanes for jet aircraft engines or powergeneration turbine components. The disclosure also relates to thecoating of an integrated core-shell mold with a ceramic outer layer,which may provide any one or combination of the following exemplarybenefits: to increase structural integrity of the core-shell mold; tobond or connect portions of the mold; to provide passageways or cavitiesin fluid communication with the mold; to control structural propertiesof the mold; and/or to control thermal properties of the mold.

BACKGROUND

A gas turbine engine generally includes at least one compressor topressurize air to be channeled into a combustor. The engine may includeat least one combustor in which at least a portion of the channeledpressurized air is mixed with fuel and ignited. Hot gasses from thecompressor flow downstream through at least one turbine section. Eachturbine section has rotating blades rotating about an axis and containedwithin an engine housing. The turbine section or sections may power anyone of the compressor, a fan, a shaft, and/or may provide thrust throughexpansion through a nozzle, for example.

The turbine blades and/or stator vanes in the turbine portions must beable to withstand thermal stresses due to high temperatures and largetemperature fluctuations as well as forces due to the high rotationalspeed experienced during normal operation of the turbine. As thepressure ratio and efficiency of turbines have increased, the thermalstresses the high pressure and low pressure turbine portions are exposedto have also increased. Accordingly, in combination with manufacturingcomponents of the turbine (e.g. turbine blades and stator vanes) from ahigh-temperature resistant material, effective cooling of the turbineblades, stator vanes and other components have become increasinglyimportant and challenging. To counteract the radiation and convection ofheat to the turbine section, several heat removal techniques have beenemployed in the past; fluid cooling is generally employed to prolong thelife of the turbine components. Further, small cooling holes have beendrilled though the blade at angles optimized to remove heat and providea thermal barrier on the surface of each airfoil surface of the turbineblades and stator vanes. Passages are also formed within the turbineand/or stator vanes to provide convection cooling of the surface of eachairfoil.

The desire for increased cooling efficiency within turbine engine hasled to complex internal cooling passages within turbine components.Conventional techniques for manufacturing engine parts and componentsinvolve the process of investment or lost-wax casting. One example ofinvestment casting involves the manufacture of a typical blade used in agas turbine engine. A turbine blade and/or stator vane typicallyincludes hollow airfoils that have radial channels extending along thespan of a blade having at least one or more inlets for receivingpressurized cooling air during operation of the engine. Various coolingpassages in a blade typically include a serpentine channel disposed inthe middle of the airfoil between the leading and trailing edges. Theairfoil typically includes inlets extending through the blade forreceiving pressurized cooling air, which include local features such asshort turbulator ribs or pins for increasing the heat transfer betweenthe heated sidewalls of the airfoil and the internal cooling air.

The manufacture of these turbine blades, typically from high strength,superalloy metal materials, involves numerous steps as shown in FIGS.1-4. As shown in FIG. 1, forming a cast component using traditionalinvestment casting typically includes steps of: machining of dies forthe outer wax structure and for ceramic cores 101, molding and firingthe ceramic cores 102, molding a wax pattern with ceramic core 103, waxassembly prep 104, dipping the wax assembly in ceramic slurry 105,drying the ceramic slurry to provide a shell 106, dewaxing the shell107, casting and leaching 108, and drilling cooling holes 109.

In the abovementioned process, a precision ceramic core 200 ismanufactured to conform to the serpentine cooling passages desiredinside the turbine blade. A precision die or mold is also created whichdefines the precise 3-D external surface of the turbine blade includingits airfoil, platform, and integral dovetail. The ceramic core 200 isassembled inside two die halves which form a space or void therebetweenthat define the resulting metal portions of the blade. A relativelyrigid wax and/or plastic is injected into the assembled dies to fill thevoid and surround the ceramic core 200, at which point the ceramic core200 is encapsulated within the wax. The two die halves are split apartand removed to expose and remove the rigid wax and/or plastic that hasthe precise configuration of the desired blade formed of a molded wax211. The molded wax blade 211 with encapsulated ceramic core 200 is thenattached to a wax tree structure 212. The wax tree structure 212 isformed of a paraffin wax or any wax that is less rigid than the wax usedto form the molded wax blade 211. Because the wax of the wax tree 212will ultimately define a flowpath for molten metal into the ceramicmold, the dimensional accuracy of the outer surface of the wax used toform the tree structure 212 is less crucial. Thus, a softer wax isgenerally used to form the individual paths of the wax tree 212 than forthe precisely molded wax blade 211 of the desired wax blade. The waxblade 211 requires pins 205 for holding the core in place. The treestructure 212 may include a funnel shaped portion 214 for adding moltenmetal to the mold. As shown in FIGS. 2-4, the tree structure 212 alsoincludes a ceramic filter 213 for filtration of molten metal in thecasting operation.

Ceramic filters generally known in the art include ceramic foam filters(CFF) like the ceramic filter 213 as shown in FIGS. 2-3. These filtersare formed by impregnating reticulated polyurethane foam with ceramicslip, removing the excess slip by squeezing the foam, and then dryingand firing the body forming a CFF. Other known ceramic filters includesymmetric filters. More recently, ceramic filters have been made usingvarious additive technologies. For example, U.S. Patent Application Pub.No. 2016/0038866 A1 entitled “ceramic filters” describes an additivelymanufactured ceramic filter. Another example is “Advanced Filtration toImprove Single Crystal Casting Yield—Mikro Systems,” available at theNational Energy Technology Laboratory (NETL) website. These filters aresold as stand-alone filters that may be incorporated in the wax tree 212as shown in FIG. 2, and then incorporated into the ceramic mold as shownin FIG. 3.

After wax injection and the attachment of wax passageways which form thewax tree structure, the entire wax tree structure 212, ceramic filter213, and wax turbine blade 211 is then coated with a ceramic material toform a ceramic shell 206, 204 as shown in FIGS. 3 and 4. Then, the waxis melted and removed from the ceramic shell 206, leaving acorresponding void or space 201, 207 between the ceramic shell 206 andthe internal ceramic core 200. Further, once the wax tree structure 212is melted, the ceramic shell 204 defines a flow path in fluidcommunication with the void or space 201, 207. After the wax is removed,the ceramic core is held in place by pins 205. As shown in FIG. 4,molten superalloy metal 208 is then poured into the shell 206 throughthe flow path defined by a portion of the ceramic shell 204. The moltensuperalloy may include any one of stainless steel, aluminum, titanium,Inconel 625, INCONEL®718, INCONEL®188, cobalt chrome, nickel, amongother metal materials or any alloy; such as nickel (Ni) superalloys,and/or Ni superalloy single crystal alloys. For example, the abovealloys may include materials with trade names, Haynes 188®, Haynes 625®,Super Alloy INCONEL®625™, Chronin® 625, Altemp® 625, Nickelvac® 625,Nicrofer® 6020, INCONEL®188, and any other material having materialproperties attractive for the formation of components using theabove-mentioned techniques. The molten superalloy metal 208 fills thevoids 201, 207 and encapsulates the ceramic core 200 contained in theshell 206. The molten metal 208 is cooled and solidifies, and then theexternal ceramic shell 206 and internal ceramic core 202 are suitablyremoved leaving behind the desired metallic turbine blade in which theinternal cooling passages are found. In order to provide a pathway forremoving the ceramic core material via a leaching process, a ball chute(not shown) and the tip pins (e.g. reference 505 in FIG. 11) must beprovided. Generally, after the leaching process, a ball chute and tippin holes within the turbine blade must be subsequently brazed shut.

The cast turbine blade 208 typically undergoes additional post-castingmodifications, such as drilling of suitable rows of film cooling holesthrough the sidewalls of the airfoil as desired for providing outletsfor the internally channeled cooling air which then forms a protectivecooling air film or blanket (generally referred to as film cooling) overthe external surface of the airfoil during operation in the gas turbineengine. After the turbine blade is removed from the ceramic mold, pins205 which held the ceramic core 200 form a passageway that is laterbrazed shut to provide the desired pathway of air through the internalvoids of the cast turbine blade. However, these post-castingmodifications are limited and given the ever increasing complexity ofturbine engines and the recognized efficiency improvements provided bycertain cooling circuits inside turbine blades, more complicated andintricate internal geometries are required. While investment casting iscapable of manufacturing these parts, positional precision and intricateinternal geometries become more complex to manufacture using theseconventional manufacturing processes and thus increase manufacturingtime and expense significantly. Accordingly, it was desirable to providean improved casting method for three dimensional components havingintricate internal voids and cooling circuits.

Additive manufacturing techniques, and 3-D printing allowed molds to bemanufactured without the toolpath and/or molding limitations associatedwith subtractive manufacturing. For example, methods for using 3-Dprinting to produce a ceramic core-shell mold are described in U.S. Pat.No. 8,851,151 assigned to Rolls-Royce Corporation. The methods formaking the molds include powder bed ceramic processes such as disclosedU.S. Pat. No. 5,387,380 assigned to Massachusetts Institute ofTechnology, and selective laser activation (SLA) such as disclosed inU.S. Pat. No. 5,256,340 assigned to 3D Systems, Inc. The ceramiccore-shell molds according to the '151 patent are significantly limitedby the printing resolution capabilities of these processes. As shown inFIG. 5, core portion 301 and shell portion 302 of integrated core-shellmold 300 is held together via a series of tie structures 303 provided atthe bottom edge of the mold 300. Cooling passages are proposed in the'151 patent that include staggered vertical cavities joined by shortcylinders, the length of which is nearly the same as its diameter. Asuperalloy turbine blade is then formed in the core-shell mold usingknown techniques disclosed in the '151 patent, and incorporated hereinby reference. After a turbine blade is cast in one of these core-shellmolds, the mold is removed to reveal a cast superalloy turbine blade.

There still remains the need to prepare ceramic core-shell moldsproduced using higher resolution methods that are capable of providingfine detail cast features in the end-product of the casting process suchas fine resolution capability necessary to print filaments extendingbetween the core and shell portion of the mold of sufficiently smallsize and quantity to result in effusion cooling holes in the finishedturbine blade or stator vane, for example. In the case of earlier powderbed processes, such as disclosed in U.S. Pat. No. 5,387,380 assigned toMassachusetts Institute of Technology, the action of the powder bedrecoater arm precludes formation of sufficiently fine filamentsextending between the core and shell to provide an effusion cooling holepattern in the cast part. Other known techniques such as selective laseractivation (SLA) such as disclosed in U.S. Pat. No. 5,256,340 assignedto 3D Systems, Inc. that employ a top-down irradiation technique may beutilized in producing an integrated core-shell mold in accordance withthe present invention. However, the available printing resolution ofthese systems significantly limits the ability to make filaments ofsufficiently small size to serve as effective cooling holes in the castfinal product.

While the above-mentioned processes can be used to form integratedcore-shell mold, it is advantageous to manufacture a core-shell moldusing direct light processing (DLP). DLP differs from the abovediscussed powder bed and SLA processes in that the light curing of thepolymer occurs through a window at the bottom of a resin tank thatprojects light upon a build platform that is raised as the process isconducted. With DLP an entire layer of cured polymer is producedsimultaneously, and the need to scan a pattern using a laser iseliminated. Further, the polymerization occurs between the underlyingwindow and the last cured layer of the object being built. Theunderlying window provides support allowing thin filaments of materialto be produced without the need for a separate support structure. Inother words, producing a thin filament of material bridging two portionsof the build object is difficult and was typically avoided in the priorart. For example, the '151 patent discussed above in the backgroundsection of this application used vertical plate structures connectedwith short cylinders, the length of which was on the order of theirdiameter. Staggered vertical cavities are necessitated by the fact thatthe powder bed and SLA techniques disclosed in the '151 patent requirevertically supported ceramic structures and the techniques are incapableof reliably producing filaments. For example, round cooling holesgenerally have a diameter of less than 2 mm corresponding to a coolinghole area below 3.2 mm². Production of a hole of such dimensionsrequires a resolution far below the size of the actual hole given theneed to produce the hole from several voxels. This resolution is simplynot available in a powder bed process. Similarly, stereolithography islimited in its ability to produce such filaments due to lack of supportand resolution problems associated with laser scattering. But the factthat DLP exposes the entire length of the filament and supports itbetween the window and the build plate enables producing sufficientlythin filaments spanning the entire length between the core and shell toform a ceramic object having the desired cooling hole pattern. Althoughpowder bed and SLA may be used to produce filaments, their ability toproduce sufficiently fine filaments as discussed above is limited.

Further, in employing the above-mentioned DLP method of manufacturing acore-shell of the embodiment described above, various difficulties arisein integrating the use of a core-shell mold into an efficientmanufacturing process. For example, the time required to form acore-shell mold having sufficient dimensional stability (e.g., wallthickness) using a DLP process may delay the manufacturing process andrequire the use of excess material. Further, in the molding process itmay be desired to efficiently produce portions of a mold that do notrequire the same dimensional accuracy as is required in portions of thecore-shell mold itself. For example, it may be desirable to producepassages for directing the flow of molten superalloy into a single orplurality of core-shell molds. Further, when forming a core-shell moldusing a DLP process it may be desirable to improve the ease of removingthe core-shell once the casting is completed. For example, the knockoutprocess may be improved by producing a thinner core-shell, to reduce thelikeliness that the cast product is damaged upon removal of thecore-shell. It may also be desirable to control the thermal conductivityof the core-shell mold to control crystal growth and/or tailor thematerial properties of the cast component.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, the invention relates to a method of fabricating aceramic casting mold. The foregoing and/or other aspects of the presentinvention may be achieved by a method of fabricating a ceramic castingmold including connecting at least one wax gate component to a ceramiccore-shell mold, the ceramic core-shell mold including a core portionand a shell portion and at least one first cavity between the coreportion and the shell portion. The method further includes coating atleast a portion of the ceramic core-shell mold and the wax gatecomponent with a second ceramic material and removing the wax gatecomponent to form at least a second cavity in fluid communication withthe first cavity.

The core-shell mold may be fabricated through the use of additivemanufacturing techniques. More specifically the method may comprisemaking a ceramic mold having a core and shell. The method having stepsof (a) contacting a cured portion of a workpiece with a liquid ceramicphotopolymer; (b) irradiating a portion of the liquid ceramicphotopolymer adjacent to the cured portion through a window contactingthe liquid ceramic photopolymer; (c) removing the workpiece from theuncured liquid ceramic photopolymer; and (d) repeating steps (a)-(c)until a ceramic mold is formed. After step (d), the process may furtherinclude a step (e) of pouring a liquid metal into a casting mold andsolidifying the liquid metal to form the cast component. After step (e),the process may further include a step (f) comprising removing the moldfrom the cast component, and this step preferably involves a combinationof mechanical force and chemical leaching in an alkaline bath. By addinga second ceramic material on at least a portion of the ceramic mold instep (d), at least one of the following advantages can be achieved:improvement of the structural integrity of the mold; reduction in buildtime of the core and shell; reduction in materials required to form themold; ability to tailor the material properties of the mold; ability totailor the thermal properties of the mold; and/or improvement in castingefficiency and/or production.

In another aspect, the invention relates to a method of preparing a castcomponent. The method includes steps of pouring a liquid metal into aceramic casting mold and solidifying the liquid metal to form the castcomponent, the ceramic casting mold comprising a core portion and afirst ceramic shell portion and a second ceramic shell portionsurrounding at least a portion of the first ceramic shell portion,wherein the ceramic casting mold has at least one cavity between thecore portion and the first ceramic shell portion, the cavity adapted todefine the shape of the cast component upon casting and removal of theceramic mold. Further, the ceramic casting mold may include a pluralityof filaments joining the core portion and the first ceramic shellportion where each filament spans between the core and the first ceramicshell, the filaments adapted to define a plurality of holes in the castcomponent upon removal of the mold. The invention may further comprisethe step of removing the ceramic casting mold from the cast component byleaching at least a portion of the ceramic core through the holes in thecast component provided by the filaments.

In one embodiment, the invention relates to a method for fabricating aceramic mold, comprising: (a) contacting a cured portion of a workpiecewith a liquid ceramic photopolymer; (b) irradiating a portion of theliquid ceramic photopolymer adjacent to the cured portion through awindow contacting the liquid ceramic photopolymer; (c) removing theworkpiece from the uncured liquid ceramic photopolymer; and (d)repeating steps (a)-(c) until a first ceramic mold formed of a firstceramic material is formed, and (e) adding a second ceramic material onat least a portion of the first ceramic mold to form an outer mold. Theouter ceramic mold encasing the first ceramic mold and the filterportion; the first ceramic mold comprising a core portion and a shellportion with at least one cavity between the core portion and the shellportion, the cavity adapted to define the shape of a cast component uponcasting and removal of the ceramic mold and the filter portion orientedin the path of molten metal flowing into the cavity of the mold. Theprocess further includes, after step (e), a step (f) comprising pouringa liquid metal into a casting mold and solidifying the liquid metal toform the cast component. After step (f), a step (g) including removingthe mold from the cast component may be performed.

In another embodiment, the invention relates to a method of preparing acast component using an additively manufactured mold. The methodincludes using the abovementioned steps to form a first ceramic shellportion of a partial ceramic mold formed of a first ceramic material andoptionally forming a first ceramic core portion, the optional firstceramic core portion and the first ceramic shell portion adapted tointerface with at least an optional second ceramic core portion and asecond ceramic shell portion to form at least a two piece ceramic moldcomprising a cavity between the first and/or second ceramic coreportions and the first and second shell portions, the cavity adapted todefine a cast component upon casting and removal of the ceramic mold.The first and second ceramic shell portions are then assembled via theinterface and a third ceramic shell is formed on at least a portion ofthe first and/or second ceramic shell portion. A liquid metal isprovided so as to fill the cavity. The ceramic is subsequently removedand a portion of the ceramic core is leached through at least one holein the cast component.

In another embodiment, the invention relates to a method of forming amold using any of the abovementioned techniques, wherein the outerceramic shell portions are provided so as to increase or decrease thethermal conductivity of at least a portion of the mold. Further, theouter ceramic shell may be provided in such a way as to provide variablethermal conductivity to the mold. For example, a thickness of the moldmay be varied, porosity of the outer layer of the mold may be varied,the material properties of various portions of the ceramic mold may bevaried, and/or a combination of the abovementioned variables may bealtered to control the thermal properties of the mold. Further, thethermal properties of the mold may be tailored to control crystallinegrowth or directionality of the cast component to be produced in themold.

In another embodiment, a method of fabricating a ceramic casting mold isdisclosed. The method comprises steps of: covering or plugging anopening in a ceramic core-shell mold with a cover or a plug, the ceramiccore-shell mold comprising a core portion and a shell portion and atleast one first cavity between the core portion and the shell portion;and coating at least a portion of the ceramic core-shell mold and thecover or plug with a second ceramic material.

In another aspect, a method of forming a cast component is disclosed.The method comprises steps of: covering or plugging an opening in aceramic core-shell mold with a cover or a plug, wherein the core-shellmold includes at least a first cavity between a ceramic core and aceramic shell; coating at least a portion of the ceramic core-shell moldand the cover or plug with a ceramic outer shell formed of a secondceramic material; and pouring a molten metal into the first cavity.

In another embodiment, a ceramic casting mold is disclosed. The ceramiccasting mold comprises: a ceramic core portion, a first ceramic shellportion, a ceramic cover, and a second ceramic shell portion at leastpartially covering the first ceramic shell portion and the ceramiccover. The ceramic casting mold further comprises; at least one cavitybetween the ceramic core portion and the first ceramic shell portion,the cavity adapted to define the shape of the cast component uponcasting and removal of the ceramic casting mold. The mold furthercomprises a plurality of filaments joining the ceramic core portion andthe first ceramic shell portion where each filament spans between theceramic core and first ceramic shell portion, the filaments adapted todefine a plurality of holes providing fluid communication between acavity within the cast component defined by the ceramic core portion andan outer surface of the cast component upon removal of the mold.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and constitute apart of this specification, illustrate one or more example aspects ofthe present disclosure and, together with the detailed description,serve to explain their principles and implementations.

FIG. 1 is a flow diagram showing the steps for conventional investmentcasting;

FIG. 2 is a schematic diagram showing a conventional wax patternattached to a wax tree structure for investment casting of a turbineblade;

FIG. 3 is a schematic diagram showing the conventional ceramic mold ofFIG. 2 after the wax has been removed;

FIG. 4 is a schematic diagram showing the conventional ceramic mold ofFIG. 2 after molten metal is poured into the mold;

FIG. 5 shows a perspective view of a prior art integrated core-shellmold with ties connecting the core and shell portions;

FIGS. 6-9 show schematic lateral sectional views of a device forcarrying out successive phases of the method sequence for direct lightprocessing (DLP);

FIG. 10 shows a schematic sectional view along the line A-A of FIG. 9;

FIG. 11 shows a cross-section view of an integrated core-shell mold withfilaments connecting the core and shell portions;

FIG. 12 is a flowchart showing the casting process according to oneaspect of the present invention;

FIG. 13 shows a cross-section side view of an integrated core-shell moldaccording to an embodiment of the present invention;

FIG. 14 shows an cross-section side view of an integrated core-shellmold having an outer ceramic layer according to an embodiment of thepresent invention;

FIG. 15 shows a cross-section side view of a superalloy filledintegrated core-shell mold according to an embodiment of the presentinvention;

FIG. 16 shows a turbine blade produced using the mold of FIGS. 14 and15;

FIG. 17 shows a schematic side view of an integrated core-shell moldwith an integrated filter and filaments connecting the core and shellportions of the integrated mold in accordance with another aspect of thepresent invention;

FIG. 18 shows a cross-section side view of FIG. 17 having an outerceramic layer according to one embodiment of the present invention;

FIG. 19 shows a cross-section side view of a two-part integralcore-shell mold including filaments extending from the core to the shellfor in accordance with an embodiment of the invention;

FIG. 20 shows a cross-section side view of an assembled two-partintegral core-shell mold of FIG. 19 and having an outer ceramic coatingapplied in accordance with an embodiment of the invention;

FIG. 21 shows a cross-section side view of a two-part integralcore-shell mold including filaments extending from the core to the shellin accordance with an embodiment of the invention;

FIG. 22 shows a cross-section side view of an assembled two-partintegral core-shell mold of FIG. 21 and having an outer ceramic coatingapplied in accordance with an embodiment of the invention;

FIG. 23 shows a cross-section side view of an integral core-shell moldhaving an opening and a plug in accordance with one embodiment of theinvention;

FIG. 24 shows a cross-section side view of the integral core-shell moldof FIG. 23 and having a plug installed in accordance with one embodimentof the invention;

FIG. 25 shows a cross-section side view of the integral core-shell moldof FIG. 24 and having an outer ceramic shell in accordance with anembodiment of the invention;

FIG. 26 shows a cross-section view of the integral core-shell mold ofFIG. 25 and having the plug removed in accordance with an embodiment ofthe invention;

FIG. 27 shows a cross-section view of an integrated core-shell moldhaving an opening and a ceramic cover plate in accordance with anembodiment of the invention;

FIG. 28 shows a cross-section view of the integrated core-shell mold ofFIG. 27 and having the ceramic cover plate installed to cover theopening;

FIG. 29 shows a cross-section view of the integrated core-shell mold ofFIG. 28 and having an outer ceramic shell in accordance with anembodiment of the invention.

DETAILED DESCRIPTION

While the aspects described herein have been described in conjunctionwith the example aspects outlined above, various alternatives,modifications, variations, improvements, and/or substantial equivalents,whether known or that are or may be presently unforeseen, may becomeapparent to those having at least ordinary skill in the art.Accordingly, the example aspects, as set forth above, are intended to beillustrative, not limiting. Various changes may be made withoutdeparting from the spirit and scope of the disclosure. Therefore, thedisclosure is intended to embrace all known or later-developedalternatives, modifications, variations, improvements, and/orsubstantial equivalents.

For example, the present invention provides a preferred method formaking cast metal parts, and preferably those cast metal parts used inthe manufacture of jet aircraft engines. Specifically, the production ofsingle crystal, nickel-based superalloy cast parts such as turbineblades, vanes, combustors, fuel nozzles, and shroud components can beadvantageously produced in accordance with this invention. However,other cast metal components may be prepared using the techniques andintegrated ceramic molds of the present invention.

It is recognized that prior processes known for making integratedcore-shell molds lacked the fine resolution capability necessary toprint filaments extending between the core and shell portion of the moldof sufficiently small size and quantity to result in effusion coolingholes in the finished turbine blade. Thus a core-shell mold may bemanufactured using direct light processing (DLP). DLP differs from moretraditional powder bed and SLA processes in that the light curing of thepolymer occurs through a window at the bottom of a resin tank thatprojects light upon a build platform that is raised as the process isconducted. With DLP an entire layer of cured polymer is producedsimultaneously, and the need to scan a pattern using a laser iseliminated. Further, the polymerization occurs between the underlyingwindow and the last cured layer of the object being built. Theunderlying window provides support allowing thin filaments of materialto be produced without the need for a separate support structure. Inother words, producing a thin filament of material bridging two portionsof the build object is difficult and was typically avoided in the priorart. For example, the '151 patent discussed above in the backgroundsection of this application used vertical plate structures connectedwith short cylinders, the length of which was on the order of theirdiameter. Staggered vertical cavities are necessitated by the fact thatthe powder bed and SLA techniques disclosed in the '151 patent requirevertically supported ceramic structures and the techniques are incapableof reliably producing filaments. For example, round cooling holesgenerally have a diameter of less than 2 mm corresponding to a coolinghole area below 3.2 mm². Production of a hole of such dimensionsrequires a resolution far below the size of the actual hole given theneed to produce the hole from several voxels. This resolution is simplynot available in a powder bed process. Similarly, stereolithography islimited in its ability to produce such filaments due to lack of supportand resolution problems associated with laser scattering. But the factthat DLP exposes the entire length of the filament and supports itbetween the window and the build plate, enables producing sufficientlythin filaments spanning the entire length between the core and shell toform a ceramic object having the desired cooling hole pattern. Althoughpowder bed and SLA may be used to produce filaments, their ability toproduce sufficiently fine filaments as discussed above is limited.

One suitable DLP process is disclosed in U.S. Pat. No. 9,079,357assigned to Ivoclar Vivadent AG and Technische Universitat Wien, as wellas WO 2010/045950 A1 and US 2011310370, each of which are herebyincorporated by reference and discussed below with reference to FIGS.6-10. In accordance with an exemplary embodiment of the presentinvention with reference to FIGS. 6-10, for example, an apparatusincludes a tank 404 having at least one translucent bottom 406 coveringat least a portion of an exposure unit 410. The exposure unit 410 mayinclude, for example, a light source and modulator with which theintensity can be adjusted position-selectively under the control of acontrol unit, in order to produce an exposure field on the tank bottom406 with the geometry desired for the layer currently to be formed. Asan alternative, a laser may be used in the exposure unit 410, the lightbeam of which successively scans the exposure field with the desiredintensity pattern by means of a mobile mirror, which is controlled by acontrol unit.

Opposite the exposure unit 410, a production platform 412 is providedabove the tank 404; it is supported by a lifting mechanism (not shown)so that it is held in a height-adjustable way over the tank bottom 406in the region above the exposure unit 410. The production platform 412may likewise be transparent or translucent in order that light can beshone in by a further exposure unit, for example, above the productionplatform 412 in such a way that, at least when forming the first layeron the lower side of the production platform 412, it can also be exposedfrom above so that the layer cured first on the production platformadheres thereto with even greater reliability.

The tank 404 contains a filling of highly viscous photopolymerizablematerial 420. The material level of the filling is much higher than thethickness of the layers which are intended to be defined forposition-selective exposure. In order to define a layer ofphotopolymerizable material, the following procedure is adopted. Theproduction platform 412 is lowered by the lifting mechanism in acontrolled way so that (before the first exposure step) its lower sideis immersed in the filling of photopolymerizable material 420 andapproaches the tank bottom 406 to such an extent that precisely thedesired layer thickness A (see FIG. 7) remains between the lower side ofthe production platform 412 and the tank bottom 406. During thisimmersion process, photopolymerizable material is displaced from the gapbetween the lower side of the production platform 412 and the tankbottom 406. After the layer thickness A has been set, the desiredposition-selective layer exposure is carried out for this layer, inorder to cure it in the desired shape. Particularly when forming thefirst layer, exposure from above may also take place through thetransparent or translucent production platform 412, so that reliable andcomplete curing takes place particularly in the contact region betweenthe lower side of the production platform 412 and the photopolymerizablematerial, and therefore good adhesion of the first layer to theproduction platform 412 is ensured. After the layer has been formed, theproduction platform 412 is raised again by means of the liftingmechanism.

These steps are subsequently repeated several times, the distance fromthe lower side of the layer 422 formed last to the tank bottom 406respectively being set to the desired layer thickness A, and the nextlayer thereupon being cured position-selectively in the desired way.

After the production platform 412 has been raised following an exposurestep, there is a material deficit in the exposed region as indicated inFIG. 6. This is because after curing the layer set with the thickness A,the material of this layer is cured and raised with the productionplatform 412 and the part of the shaped body already formed thereon. Thephotopolymerizable material therefore missing between the lower side ofthe already formed shaped body part and the tank bottom 406 must befilled from the filling of photopolymerizable material 420 from theregion surrounding the exposed region. Owing to the high viscosity ofthe material, however, it does not flow by itself back into the exposedregion between the lower side of the shaped body part and the tankbottom, so that material depressions or “holes” can remain here.

In order to replenish the exposure region with photopolymerizablematerial, an elongate mixing element 432 is moved through the filling ofphotopolymerizable material 420 in the tank 404. In the exemplaryembodiment represented in FIGS. 6 to 8, the mixing element 432 includes,for example, an elongate wire (not shown) which is tensioned betweensupport arms 430 mounted movably on the side walls of the tank 404. Thesupport arms 430 may be mounted movably in guide slots 434 in the sidewalls of the tank 404, so that the wire tensioned between the supportarms 430 can be moved relative to the tank 404, parallel to the tankbottom 406, by moving the support arms 430 in the guide slots 434. Theelongate mixing element 432 has dimensions and its movement is guidedrelative to the tank bottom 406, such that the upper edge of theelongate mixing element 432 remains above the material level of thefilling of photopolymerizable material 420 in the tank outside theexposed region. As can be seen in the sectional view of FIG. 8, themixing element 432 is below the material level in the tank over theentire length of the wire, and only the support arms 430 protrude beyondthe material level in the tank. The effect of arranging the elongatemixing element 432 below the material level in the tank 404 is not thatthe elongate mixing element 432 substantially moves material in front ofit during its movement relative to the tank through the exposed region,but rather this material flows over the mixing element 432 whileexecuting a slight upward movement. The movement of the mixing element432 from the position shown in FIG. 8 to, for example, a new position isshown in FIG. 9. It has been found that by this type of action on thephotopolymerizable material in the tank, the material is effectivelystimulated to flow back into the material-depleted exposed regionbetween the production platform 412 and the exposure unit 410.

The movement of the elongate mixing element 432 relative to the tank 404may be carried out by a linear drive which moves the support arms 430along the guide slots 434 in order to achieve the desired movement ofthe elongate mixing element 432 through the exposed region between theproduction platform 412 and the exposure unit 410. As shown in FIG. 8,the tank bottom 406 has recesses 406′ on both sides. The support arms430 project with their lower ends into these recesses 406′. This makesit possible for the elongate mixing element 432 to be held at the heightof the tank bottom 406, without interfering with the movement of thelower ends of the support arms 430 through the tank bottom 406.

Other alternative methods of DLP may be used to prepare the integratedcore-shell molds of the present invention. For example, the tank may bepositioned on a rotatable platform. When the workpiece is withdrawn fromthe viscous polymer between successive build steps, the tank may berotated relative to the platform and light source to provide a freshlayer of viscous polymer in which to dip the build platform for buildingthe successive layers. Further, the integrated core-shell mold may beformed using any well known method in the art.

FIG. 11 shows a schematic side view of an integrated core-shell moldwith filaments 502 connecting the core 500 and shell portions 501. Byprinting the ceramic mold using the above DLP printing process, the moldcan be made in a way that allows the point of connections between thecore and shell to be provided through filaments 502. Once the core-shellmold is printed, it may be subject to a post-heat treatment step to curethe printed ceramic polymer material. The cured ceramic mold may then beused similar to the traditional casting process used in the productionof superalloy turbine blades, vanes, or shrouds. Notably because thefilaments 502 are provided in a large quantity consistent with formationof a pattern of effusion cooling holes in the surface of a turbine bladeor vane, the need for pins shown in FIG. 3, or a ball chute structuremay be eliminated. In this embodiment, the tip pins 505 connecting thetip plenum core 504 to the core 500 are retained, and a void 503 existsbetween the shell portion 501 and the tip plenum core 504. After removalof the ceramic mold, tip holes exist between the core 500 and tip plenumcore 504 that may be subsequently brazed shut. However, the tip pins 505may be eliminated, avoiding the need to braze shut tip holes connectingthe core cavity with the tip plenum.

The filaments 502 are preferably cylindrical or oval shape but may alsobe curved or non-linear. Their exact dimensions may be varied accordingto a desired film cooling scheme for a particular cast metal part. Forexample, cooling holes may have a cross sectional area ranging from 0.01to 2 mm². In a turbine blade, the cross sectional area may range from0.01 to 0.15 mm², more preferably from 0.05 to 0.1 mm², and mostpreferably about 0.07 mm². In the case of a vane or a shroud, thecooling holes may have a cross sectional area ranging from 0.05 to 0.2mm², more preferably 0.1 to 0.18 mm², and most preferably about 0.16mm². The spacing of the cooling holes is typically a multiple of thediameter of the cooling holes ranging from 2× to 10× the diameter of thecooling holes, most preferably about 4-7× the diameter of the holes.

The length of the filament 502 is dictated by the thickness of the castcomponent, e.g., turbine blade or stator vane wall thickness, and theangle at which the cooling hole is disposed relative to the surface ofthe cast component. The typical lengths range from 0.5 to 5 mm, morepreferably between 0.7 to 1 mm, and most preferably about 0.9 mm. Theangle at which a cooling hole is disposed is approximately 5 to 35°relative to the surface, more preferably between 10 to 20°, and mostpreferably approximately 12°. It should be appreciated that the methodsof casting according to the present invention allow for formation ofcooling holes having a lower angle relative to the surface of the castcomponent than currently available using conventional machiningtechniques.

As shown in FIG. 12, by employing the DLP process or any other additivemanufacturing method to form a ceramic core-shell mold, themanufacturing of a component requires significantly less steps thantypical investment casting, as discussed above in the backgroundsection. In accordance with an embodiment of the present invention, FIG.12 shows the steps of forming ceramic mold and core using additivemanufacturing 601, prepping the wax assembly 602, dipping the core-shellmold into a ceramic slurry 603, drying the slurry 604, a dewaxing and/orfiring process 605, and casting and leaching the ceramic material 606.It may be appreciated that the step of dipping the core-shell mold intothe ceramic slurry 603 and drying the slurry 604 may be repeated asshown in FIG. 12. The above-mentioned process of forming a mold mayinclude forming a ceramic mold and core using an DLP process such thatthe mold is formed as a core-shell structure and is formed of a firstphotopolymerizable ceramic material. Once a mold is formed, the mold maybe joined with several molds and/or may have a wax portion added 602which will form a flow path for the molten material. The core-shell moldand any additional wax structures added previously may then undergo adipping or coating process 603 to form a ceramic coating on the outersurface of the shell of the core-shell mold and on the outer surface ofany added wax structures. The core-shell mold may then undergo a dryingprocess to the dry the slurry 604. As mentioned above, steps 603 and 604may be repeated. Then, the core-shell mold and outer ceramic shell mayundergo a dewaxing and/or firing process 605 to remove the wax and/or tosinter the ceramic materials which form the mold. It may be appreciatedthat steps 602, 603, 604, and 605 may be omitted if the ceramic mold andcore in step 601 is manufactured to the final mold shape and ready forpouring. The molten superalloy may then be poured into the mold. Oncethe superalloy has solidified, the core-shell mold and outer shell maybe removed through either leaching of the ceramic material and/orthrough mechanical removal (e.g. knockoff) of the mold.

FIG. 13 shows a side view of an integrated core-shell mold according toan embodiment of the present invention. As shown in FIG. 13, the core1000 is connected to the shell 1001 through several filaments 1002. Thecore 1000 and the shell 1001 forms the core-shell mold which defines acavity 1003 for investment casting a turbine blade. The core-shell moldmay be connected to a wax gate structure, which may comprise any one ofa wax tube 1009, 1007, and/or a wax plug 1008 and/or any selectedportion of the final cast article. The core-shell mold may include apassageway 1006 in fluid communication with an inner cavity 1003 of thecore-shell mold. The passageway 1006 may have a plurality of wax gateportions 1009, 1007 attached to the core-shell mold. A hole 1006 or aplurality of holes may be integrated with a portion of the cavity 1003.Once the core-shell mold is formed and any wax gate structures areconnected to the core-shell mold, an outer ceramic layer 1004 is formedon the outer surface of the core-shell mold and wax gate structures asshown in FIG. 14. The outer ceramic layer 1004 may be formed throughdipping of the core-shell mold into a ceramic slurry. The outer ceramiclayer 1004 may further be formed as a single layer formed through thedipping of the core-shell mold and/or gate portions into a ceramicslurry, drying the slurry, and dipping the core-shell mold into a eitherthe same ceramic slurry and/or different type of slurry to form an outershell on the core-shell mold. Further, a refractory grain may be siftedonto the slurry coating between layers. It is noted that other forms offorming a ceramic coating could be used in lieu of or in combinationwith the dipping process mentioned above. For example, a ceramic and/orother material may be sprayed onto the core-shell. As an example, theabove-mentioned slurry may include colloidal silica and a ceramic powder(e.g. Al2O3, SiO2, ZrSiO4, ZrO2, Y2O3, AIN, SiC). The above-mentionedgrain may be applied between layers and may include ceramic sand (e.g.Al2O3, SiO2, ZrSiO4, ZrO2, Y2O3, AIN, SiC) in a mesh of 90-120.Subsequent layers of slurry may be applied and subsequent layers ofceramic sand may be applied in 20-70 mesh and/or 10-30 mesh. Once thenecessary outer layer is formed on the core-shell, the mold may be firedto sinter the material; after which, any of the above-mentioned metals(e.g. superalloy) may be poured into the mold.

As shown in FIG. 14, once the outer ceramic layer 1004 is formed, thewax gate portions 1007-1009 may be removed through either melting and/ora chemical removal process. Once the wax gate portions are removed, atleast a second passage is formed that is defined by the outer ceramicshell 1004 which was formed on the outer surface of the wax gateportions. The passages corresponding to the wax gate portions 1007-1009form a cavity which may be in fluid communication with the inner cavity1003 of the core-shell mold. Further, the ceramic layer 1004 may providestructural qualities to the core-shell mold and may serve as areinforcement for increasing the durability of the encased core-shellmold and may improve the thermal properties of the mold.

FIG. 15 shows the cavity 1003 as shown in FIGS. 13 and 14 filled with ametal 1005, such as a nickel based alloy, e.g., INCONEL®. Once the metalis hardened, the ceramic core and/or shell may be leached out. Uponleaching of the ceramic core-shell, the resulting cast object is aturbine blade having a cooling hole pattern in the surface of the blade.It should be appreciated that although FIGS. 11, 13-18 provide a crosssectional view showing cooling holes at the leading and trailing edge ofthe turbine blade, that additional cooling holes may be provided wheredesired including on the sides of the turbine blades or any otherlocation desired. In particular, the present invention may be used toform cooling holes within the casting process in any particular design.In other words, one would be able to produce conventional cooling holesin any pattern where drilling was used previously to form the coolingholes. However, an embodiment of the present invention allows forcooling hole patterns previously unattainable due to the limitations ofconventional technologies for creating cooling holes within castcomponents, e.g., drilling. FIG. 16 shows a cross section of the castturbine blade 1100 once the ceramic core-shell has been removed throughleaching and/or mechanical methods. The turbine blade 1100 includescooling holes 1101, 1102 connecting the blade surface to the hollow core1103 of the blade 1100.

FIG. 17 shows a schematic side view of an integrated core-shell moldwith filaments 902 connecting the core 900 and shell portions 901 of theintegrated core-shell mold in accordance with another aspect of thedisclosure. Further, the core shell mold may include a cavity 913 atleast partially defined by the core 900 and shell 901 portions of thecore-shell mold. The cavity 913, may ultimately define the structure ofthe component once the molten metal is added and solidified. By printingthe ceramic mold using the above-mentioned DLP printing process, themold can be made in a way that allows the connections between the coreand shell to be provided through filaments 902 to form cooling holes inthe finished component. Further, the filaments may be used to leach theceramic core 900 from the center of the component once casting iscomplete. Once the core-shell mold is printed, it may be subject to apost-heat treatment step to cure the printed ceramic polymer material.As shown in FIG. 17, either before or after a curing of the core-shellmold, a sacrificial gate component formed of wax, for example, may beconnected to the core-shell mold. The gate component may include aplurality of wax rods or tubes 909, 907, and/or may include a plug 903and/or an adapter 908 to connect to a filter 905. Further, as discussedbelow, the filter 905 may be formed using an additive manufacturingtechnique (e.g., DLP) and may be formed as a single structure with thecore-shell mold or may be formed separately and added to the core-shellmold.

After the gate components are added to the core-shell mold, an outerceramic layer 910 may be formed on the outer surface of the core-shellmold and/or the gate structures and/or the filter 905. As shown in FIG.18, the outer ceramic layer 910 may be formed through dipping of thecore-shell mold 901, 900, the gate components 907-909 and/or the filter905 into a ceramic slurry. The outer ceramic layer 910 may further beformed as a single layer formed through the dipping of the core-shellmold into a ceramic slurry, drying the slurry coating on the core-shell,and dipping the core-shell mold into a either the same ceramic slurryand/or different type of slurry to form an outer shell on the core-shellmold. Further, a refractory grain may be sifted or added onto the slurrycoating between layers. It is noted that other methods of forming aceramic coating could be used in lieu of or in combination with thedipping process mentioned above. For example, a ceramic and/or othermaterial may be sprayed onto the core-shell. As an example, theabove-mentioned slurry may include colloidal silica and a ceramic powder(e.g. Al2O3, SiO2, ZrSiO4, ZrO2, Y2O3, AIN, SiC). The abovementionedgrain may be applied between layers and may include ceramic sand (e.g.Al2O3, SiO2, ZrSiO4, ZrO2, Y2O3, AIN, SiC) in a mesh of 90-120.Subsequent layers of slurry may be applied and subsequent layers ofceramic sand may be applied in 20-70 mesh and/or 10-30 mesh. Once thenecessary outer layer is formed on the core-shell, the mold may be firedto sinter the material; after which, any of the above-mentioned metalsmay be poured into the mold. The cured ceramic mold may then be usedsimilar to the traditional casting process used in the production ofturbine blades, stator vanes, shrouds, and/or any other component.

As shown in FIG. 18, once the outer ceramic layer 910 is formed on theouter surface 901 of the core-shell mold, the gate portions 907-909,and/or the filter 905, the gate portions may be removed. The gateportions 907-909 may be removed through melting of the material formingthe gate components (e.g. wax) and/or may be removed through a chemicalremoval process.

As shown in FIGS. 17 and 18, the wax gate component 903 and a filter905, which may be integrated with the mold, are provided for flowingliquid metal into the integrated mold. An integrated filter 905 isprovided within the flow-path for liquid metal as shown in FIGS. 17 and18. As mentioned above, the filter may be formed as a unitary structurewith the core-shell mold or may be attached separately prior to theouter coating 910 being applied to the core-shell mold. It is furthernoted that the wax gate component 903 may include a wax and/or plastictube portion attached to the ceramic core-shell 901. Accordingly, whenthe outer ceramic layer 910 is added to the core-shell and the wax gatecomponent is removed, a passage having an inner surface geometryequivalent to the outer surface geometry of the wax gate component 903is formed by the outer ceramic layer and thus, it is unnecessary to formthe wax gate component 903 via a DLP process. Further, it is noted thatthe filter 905 may be connected and formed using the above-mentioned DLPprocess so as to be a single structure with the core-shell mold 901. Awax and or/plastic tube may then be connected to the filter 905 prior tothe addition of the outer ceramic layer 910. The wax and/or plastic tubemay further be connected to a wax and/or plastic adapter portion 908provide an interface between the filter and the wax and/or plastic tube.

The ceramic filter 905 as shown in FIGS. 17-18 is adapted for filtrationof molten metal as it is poured into the mold. The DLP process describedabove is particularly suited to provide resolution sufficient to provideporosity for a ceramic filter for filtering molten metal. The particulargeometry of the filter used in accordance with an embodiment of thepresent invention may depend upon the characteristics of the metal to beused and the design requirements of the finished product. The geometryof the conventional ceramic filters may be used. Preferably, the filterhas a cylindrical shape where the height of the cylinder is less thanthe diameter of the filter. The ceramic filter preferably includes aninlet surface and outlet surface and openings providing a pathway forliquid metal to pass from the inlet surface through the filter and thenthe outlet surface. The openings may preferably include at least 60% toat least about 90% of a total volume of the ceramic filter. Morepreferably, the openings may include at least 70% to at least about 85%of a total volume of the ceramic filter.

Further, a port (not shown), for example, may also be provided forcleaning the integrated core-shell mold before heat treatment and/ormetal addition. After printing the ceramic mold by DLP, there may beuncured resin within the mold portion or filter portion. The port, forexample, may be provided to allow a flowpath for solvent used to removeany wax or uncured resin. If desired, several cleaning ports may beprovided in the tube portion or core-shell mold portion. It is notedthat any method of closing the port may be used. For example, in oneaspect the cleaning port is merely a hole in the tube or mold portionthat can subsequently be patched with ceramic material prior to curingthe mold after the solvent cleaning step is performed.

The filaments 902 may be cylindrical or oval shaped, but may be curvedor non-linear. Their exact dimensions may be varied according to adesired film cooling and/or bore cooling scheme for a particular castmetal part. For example, cooling holes may have a cross sectional arearanging from 0.01 to 2 mm². In a turbine blade, the cross sectional areamay range from 0.01 to 0.15 mm², more preferably from 0.05 to 0.1 mm²,and most preferably about 0.07 mm². In the case of a vane or shroud, thecooling holes may have a cross sectional area ranging from 0.05 to 0.2mm², more preferably 0.1 to 0.18 mm², and most preferably about 0.16mm². The spacing of the cooling holes is typically a multiple of thediameter of the cooling holes ranging from 2× to 10× the diameter of thecooling holes, most preferably about 4-7× the diameter of the holes.

The length of the filament 902 is dictated by the thickness of the castcomponent, e.g., turbine blade or stator vane wall thickness, and theangle at which the cooling hole is disposed relative to the surface ofthe cast component. The typical lengths range from 0.5 to 5 mm, morepreferably between 0.7 to 1 mm, and most preferably about 0.9 mm. Theangle at which a cooling hole is disposed is approximately 5 to 35°relative to the surface, more preferably between 10 to 20°, and mostpreferably approximately 12°. It should be appreciated that the methodsof casting according to the present invention allow for formation ofcooling holes having a lower angle relative to the surface of the castcomponent than currently available using conventional machiningtechniques.

In accordance with another aspect, filaments may be provided simply tohold the ceramic core 900 in place while metal is poured into the mold.The core shown in FIGS. 17 and 18 may also be formed as a hollow core asan alternative or in combination with a solid core. One advantage offorming a hollow core via the above-mentioned process, is that itreduces the extent of leaching necessary to remove the core after metalcasting. In another aspect, for example, both the core and connectingfilaments may be hollow allowing rapid leaching of the ceramic moldmaterial after casting.

Upon leaching of the ceramic core-shell, the resulting cast object maybe a turbine blade having a cooling hole pattern in the surface of theblade. It should be appreciated that although FIGS. 13-18 provide across sectional view showing cooling holes at the leading and trailingedge of the turbine blade, additional cooling holes may be providedwhere desired including on the sides of the turbine blades or any otherlocation desired. In particular, the present invention may be used toform cooling holes within the casting process in any particular design.In other words, one would be able to produce conventional cooling holesin any pattern where drilling was used previously to form the coolingholes. However, the present invention will allow for cooling holepatterns previously unattainable due to the limitations of conventionaltechnologies for creating cooling holes within cast components, i.e.,drilling. As noted above, the filaments may be used to hold the core inplace during casting. In that case, the holes in the surface provided bythe filaments can be closed using a brazing or equivalent operation.

FIG. 19 shows a cross-section side view of a two-part integralcore-shell mold including filaments extending from the core to the shellin accordance with an embodiment of the invention. As shown in FIG. 19,an example of a two-part core-shell assembly 1500 having a first coreportion 1501 with attachment mechanisms (1507, 1508), a first shellportion 1502 with attachment mechanism 1511, a second core portion 1503with attachment mechanisms (1509, 1510), and a second shell portion 1504with attachment mechanism 1512. The attachment mechanisms 1507-1508 mayfurther include any structural interface that allows the attachmentmechanisms 1507 and 1508 to be joined with the desired accuracy.Examples of possible structural interfaces which are usable with thecurrent disclosure are disclosed in U.S. patent application Ser. No.15/377,796, titled “MULTI-PIECE INTEGRATED CORE-SHELL STRUCTURE FORMAKING CAST COMPONENT” with attorney docket number 037216.00033/284909,and filed Dec. 13, 2016. The disclosures of the above-mentionedapplication is incorporated herein in the entirety to the extent that itdiscloses additional aspects of core-shell molds and methods of makingthat can be used in conjunction with the core-shell molds disclosedherein.

The first core portion 1501 and first shell portion 1502 are linkedtogether with filaments 1505. The second core portion 1503 and secondshell portion 1504 are linked together with filaments 1506. Aftercasting of the metal within the core-shell mold and leaching of thefilaments (1505, 1506), the filaments (1505, 1506) define a cooling holepattern in the cast turbine blade. As described above, these structuresare preferably formed using the DLP process described in connection withFIGS. 6-10 and discussed above. By printing the ceramic mold using theabove-mentioned DLP printing process, the mold can be made in a way thatallows the point of connections between the core and shell to beprovided through the filaments 1505 and/or 1506. Once the core-shellmold is printed, it may be inspected and the attachment mechanisms1507-1512 may be joined. The attachment mechanisms may be attached usingan adhesive or may be attached simply by the interface between themechanisms (e.g., a slip fit or an interference fit). Further, the twohalves may be held together using a clamping mechanism, strap, or someother well-known method of holding two halves of a ceramic moldtogether. Additionally the mold may be formed by more than two piecesdepending on the needs of manufacturing or design of the part.

FIG. 20 shows a cross-section side view of an assembled two-partintegral core-shell mold of FIG. 19 and having an outer ceramic coatingapplied in accordance with an embodiment of the invention. As shown inFIG. 20, once the core-shell assembly 1500 molds via the attachmentmechanisms, an outer ceramic layer 1510 may be formed on shells 1502and/or 1504. It is noted that the shells 1502 and 1504 may be purposelyformed thinner than is desired for a casting process, and the outerceramic layer 1510 being formed to add structural stability to the moldand/or to hold the two core-shell mold halves together. Further, asdiscussed below, the outer ceramic layer and inner core-shell mold maybe formed to optimize the heat conduction properties of the mold (e.g.,for tailoring the microstructure of the cast super-alloy by manipulatingthe heat conduction properties of the mold). The outer ceramic layer1510 may be formed as multiple layers formed through the dipping of thecore-shell mold into a ceramic slurry, drying the slurry coating on thecore-shell, and dipping the core-shell mold into either the same ceramicslurry and/or a different type of slurry to form an outer shell on thecore-shell mold (1502 and/or 1504). Further, a refractory grain may besifted or added onto the slurry coating between layers. It is noted thatother forms of forming a ceramic coating could be used in lieu of or incombination with the dipping process mentioned above. For example, aceramic and/or other material may be sprayed onto the core-shell. As anexample, the above-mentioned slurry may include Colloidal silica and aceramic powder (e.g. Al2O3, SiO2, ZrSiO4, ZrO2, Y2O3, AIN, SiC). Theabove-mentioned grain may be applied between layers and may includeceramic sand (e.g. Al2O3, SiO2, ZrSiO4, ZrO2, Y2O3, AIN, SiC) in a meshof 90-120. Subsequent layers of slurry may be applied and subsequentlayers of ceramic sand may be applied in 20-70 mesh and/or 10-30 mesh.After printing the core-shell mold structures and either before and/orafter the outer ceramic layer 1510 is formed on the surface of the coreshell molds (1502 and/or 1504), the core-shell mold and/or the outerceramic layer 1510 may be cured and/or fired depending upon therequirements of the ceramic core photopolymer material and/or the outerceramic core material(s). Molten metal may then be poured into the moldto form a cast object in the shape and having the features provided bythe integrated core-shell mold.

As mentioned above, the filaments 1505 and 1506 are preferablycylindrical or oval shape but may be curved or non-linear. Their exactdimensions may be varied according to a desired film cooling scheme fora particular cast metal part. For example, cooling holes may have across sectional area ranging from 0.01 to 2 mm². In a turbine blade, thecross sectional area may range from 0.01 to 0.15 mm², more preferablyfrom 0.05 to 0.1 mm², and most preferably about 0.07 mm². In the case ofa vane or shroud, the cooling holes may have a cross sectional arearanging from 0.05 to 0.2 mm², more preferably 0.1 to 0.18 mm², and mostpreferably about 0.16 mm². The spacing of the cooling holes is typicallya multiple of the diameter of the cooling holes ranging from 2× to 10×the diameter of the cooling holes, most preferably about 4-7× thediameter of the cooling holes.

The length of the filaments 1505 and/or 1506 is dictated by thethickness of the cast component, e.g., turbine blade or stator vane wallthickness, and the angle at which the cooling hole is disposed relativeto the surface of the cast component. The typical lengths range from 0.5to 5 mm, more preferably between 0.7 to 1 mm, and most preferably about0.9 mm. The angle at which a cooling hole is disposed is approximately 5to 35° relative to the surface, more preferably between 10 to 20°, andmost preferably approximately 12°. It should be appreciated that themethods of casting according to an embodiment of the present inventionallow for formation of cooling holes having a lower angle relative tothe surface of the cast component than currently available usingconventional machining techniques.

FIG. 21 shows a side view of an integrated core-shell mold 1600according to an embodiment of the present invention. As shown in FIG.21, the first core portion 1601 is connected to the first shell portion1602 through several filaments 1605. Likewise, the second core portion1602 is connected to the second shell portion 1604 through severalfilaments 1606. The first core portion 1601 and the first shell portion1602 can be attached to the second core portion 1602 and the secondshell portion 1604 via attachment mechanisms 1608, 1609, 1610 and 1611to form the complete core-shell mold assembly 1600. The attachmentmechanisms 1608-1611 may further include any structural interface thatallows to the attachment mechanisms 1608-1611 to be joined with thedesired accuracy. Additionally the assembled core-shell mold may beformed by more than two pieces depending on the needs of manufacturingor design of the part. The assembled core-shell mold 1600 defines acavity 1607 for investment casting a turbine blade.

FIG. 22 shows a cross-section side view of an assembled two-partintegral core-shell mold of FIG. 21 and having an outer ceramic coatingapplied in accordance with an embodiment of the invention. As shown inFIG. 22, once the core-shell assembly 1600 molds via the attachmentmechanisms mentioned and referenced above, an outer ceramic layer 1666may be formed on shells 1602 and/or 1604. It is noted that the shells1602 and 1604 may be purposely formed thinner than is desired for acasting process, and the outer ceramic layer 1666 being formed to addstructural stability to the mold and/or to hold the two core-shell moldhalves together. Further, as discussed below, the outer ceramic layerand inner core-shell mold may be formed to optimize the heat conductionproperties of the mold (e.g., for tailoring the microstructure of thecast super-alloy by manipulating the heat conduction properties of themold). The outer ceramic layer 1666 may be formed as a multiple layersformed through the dipping of the core-shell mold into a ceramic slurry,drying the slurry coating on the core-shell, and dipping the core-shellmold into either the same ceramic slurry and/or a different type ofslurry to form an outer shell on the core-shell mold 1602 and/or 1604.Further, a refractory grain may be sifted or added onto the slurrycoating between layers. It is noted that other forms of forming aceramic coating could be used in lieu of or in combination with thedipping process mentioned above. For example, a ceramic and/or othermaterial may be sprayed onto the core-shell. As an example, theabove-mentioned slurry may include Colloidal silica and a ceramic powder(e.g. Al2O3, SiO2, ZrSiO4, ZrO2, Y2O3, AIN, SiC). The above-mentionedgrain may be applied between layers and may include ceramic sand (e.g.Al2O3, SiO2, ZrSiO4, ZrO2, Y2O3, AIN, SiC) in a mesh of 90-120.Subsequent layers of slurry may be applied and subsequent layers ofceramic sand may be applied in 20-70 mesh and/or 10-30 mesh. Afterprinting the core-shell mold structures and either before and/or afterthe outer ceramic layer 1666 is formed on the surface of the core shellmolds 1602 and/or 1604, the core-shell mold and/or the outer ceramiclayer 1666 may be cured and/or fired depending upon the requirements ofthe ceramic core photopolymer material and/or the outer ceramic corematerial(s). Molten metal may be poured into the mold to form a castobject in the shape and having the features provided by the integratedcore-shell mold.

FIG. 22 further shows the cavity 1607, which represents a void betweenthe core 1601 and the shell 1602, 1604 to be filled with a metal (anexample of which is shown as reference 1005 in FIG. 15), such as anickel based alloy, i.e., INCONEL®. Upon leaching of the ceramiccore-shell, the resulting cast object is a turbine blade, stator vane,or shroud having a cooling hole pattern in the surface of the blade,vane, or shroud. It should be appreciated that although the figures showa cross sectional view showing cooling holes at the leading and trailingedge of the turbine blade, that additional cooling holes may be providedwhere desired including on the sides of the turbine blades or any otherlocation desired. In particular, the present invention may be used toform cooling holes within the casting process in any particular design.In other words, one would be able to produce conventional cooling holesin any pattern where drilling was used previously to form the coolingholes. However, the present invention will allow for cooling holepatterns previously unattainable due to the limitations of conventionaltechnologies for creating cooling holes within cast components, i.e.,drilling. After leaching, the resulting holes in the turbine blade orstator vane from the core print filaments may be brazed shut if desired.Otherwise the holes left by the core print filaments may be incorporatedinto the design of the internal cooling passages. Alternatively, coolinghole filaments may be provided to connect the tip plenum core to theshell in a sufficient quantity to hold a tip plenum core in place duringthe metal casting step.

Any of the above-mentioned methods can further be used to optimize thematerial properties of the mold. For example, the porosity of the outerceramic layer (e.g., 910, 1004, 1510, 1666) may be optimized so as tocontrol the conduction of heat through the core-shell mold and outerceramic layer. For example, it may be desired to improve the structuralrigidity of the core-shell without having a significant impact on theheat conduction through the core-shell during the solidification of themetal within the mold; accordingly, a ceramic material having a certainporosity may be used to improve the convection of heat through thelayer. Further, the outer ceramic layer may be formed of a materialhaving a high thermal conductivity and/or may be provided as a thinnerlayer, so as to increase the rate of heat transfer and decrease theamount of time required for solidification of the metal within the mold.Conversely, it may be desired to decrease the heat transfer from themetal within the mold; accordingly, the outer ceramic layer may beprovided with a high porosity, may be a thicker layer, and/or may be amaterial having a low thermal conductivity. It may further be desired tocontrol the heat conductivity so that the rate of cooling differs alongdifferent sections of the mold. For example, one portion of thecore-shell and/or outer ceramic layer may be formed thicker or thinnerdepending the heat conduction properties that are desired in thatportion of the mold. This strategy may be used to tailor the materialproperties of the finished product. For instance, by controlling therate of cooling, the crystal growth may be controlled in thesolidification of the superalloy material within the mold. According toanother exemplary embodiment, the outer ceramic layer may include afirst portion formed of a ceramic material having a first thermalconductivity, and a second portion formed of a ceramic material having asecond thermal conductivity, wherein the first thermal conductivity andsecond conductivity differ. In any of the abovementioned examples, thethermal conductivity of the first portion and a second portion may vary±0.05% or greater. In another example, several outer ceramic layers maybe formed of ceramic materials having differing thermal conductivity tofurther control the solidification of the metal within the mold.Further, other features may be integrated into the core-shell moldand/or the outer ceramic shell to modify either the thermal propertiesand/or the structural properties of the mold. For example, thecore-shell mold may be formed with stiffening ribs on the outer shellfor tailoring the structural properties of the mold. The core-shell moldmay further include heat-sink structures such as pins to change thethermal conductivity of the core-shell mold either across the entireouter surface or in selected portions of the mold. Further, the surfaceof the core-shell mold may be provided with air gaps and/or thicker andthinner portions between the layers to alter the thermal conductivityand/or insulation qualities of the finished mold. The air gaps may beprovided throughout the entire mold or may be provided in selectedportions of the mold where it is desired to slow down heat transferduring the solidification of the metal inside the mold.

FIG. 23 shows a side view of an integrated core-shell mold according toan embodiment of the present invention. As shown in FIG. 23, the core1700 is connected to the shell 1701 through several filaments 1702. Thecore 1700 and the shell 1701 forms the core-shell mold which defines acavity 1711 for investment casting a component, which in this example isa turbine blade. The core-shell mold may be connected to a waxcomponent, which may comprise at least one of a wax gate component. Thewax gate component may comprise a wax tube 1709, 1707, and/or a wax plug1708 and/or any selected portion of the final cast article. Thecore-shell mold may include a passageway 1706 in fluid communicationwith an inner cavity 1711 of the core-shell mold. The passageway 1706may have a wax component 1709, which may include a wax gate componentsuch as a tube, for example. A hole 1706 or a plurality of holes may beintegrated with a portion of the cavity 1711. Further, the core-shellmold may include an opening 1712, which may be in fluid communicationwith the cavity 1711. At any point during the abovementioned processes aplug 1718 may be used to cover the opening 1712 prior to coating thecore-shell mold with an outer ceramic layer. The plug 1718 may be formedof a wax, a plastic, or any combination thereof. Further, the plug 1718may be formed using a 3-D printing and/or additive manufacturingprocess. The plug 1718 may have an outer surface that includes aspecific desired geometry of the outer surface of the finishedcomponent, so that that once the plug is coated with the outer ceramiclayer and removed, a specific mold geometry in the region previouslydefined by the opening 1712 is formed. The plug 1718 may also include aninternal geometry 1710, 1716 to ensure the plug is correctly placed andoriented when the plug is installed in the opening 1712 and before theouter ceramic shell is formed on a surface of the plug. For example, anotch 1716 may be formed to interface with an inner portion of the coreshell mold 1714.

The opening 1712 may be used for inspection and/or may include a portionof the mold that is desirable to have altered or changed in themanufacturing process. For example, it may be desirable to form a firstturbine blade having a first outer geometry and a second turbine bladehaving a second outer geometry while using the same core-shell mold. Thefirst and/or second external geometries may be formed by installing afirst plug having a first geometry into the opening 1712 of a firstcore-shell mold and installing a second plug having a second geometryinto the opening 1712 of a second core-shell mold, wherein the first andsecond core-shell molds have substantially identical geometries. Theplug 1718 may also be altered based on a desired change or alteration ingeometry without having to alter or form a new ceramic core-shell mold.

As shown in FIG. 24, the core-shell mold may be formed and any optionalwax component (e.g. 1703, 1706, 1707, and 1709) may be connected, andthe plug 1718 may be installed into opening 1712 of the core-shell moldprior to forming the outer ceramic layer. As shown in FIG. 25, an outerceramic layer 1704 may then be formed on the outer surface 1701 of thecore-shell mold, the plug 1718, and any wax component (e.g. 1703, 1706,1707, and 1709). The outer ceramic layer 1704 may be formed throughdipping of the core-shell mold into a ceramic slurry. The outer ceramiclayer 1704 may further be formed as a single layer formed through thedipping of the core-shell mold, the plug, and/or the gate portions intoa ceramic slurry, drying the slurry, and dipping the core-shell moldinto a either the same ceramic slurry and/or different type of slurry toform an outer shell on the core-shell mold. Further, a refractory grainmay be sifted onto the slurry coating between layers. It is noted thatother forms of forming a ceramic coating could be used in lieu of or incombination with the dipping process mentioned above. For example, aceramic and/or other material may be sprayed onto the core-shell.

As an example, the above-mentioned slurry may include colloidal silicaand a ceramic powder (e.g. Al2O3, SiO2, ZrSiO4, ZrO2, Y2O3, AIN, SiC).The above-mentioned grain may be applied between layers and may includeceramic sand (e.g. Al2O3, SiO2, ZrSiO4, ZrO2, Y2O3, AIN, SiC) in a meshof 90-120. Subsequent layers of slurry may be applied and subsequentlayers of ceramic sand may be applied in 20-70 mesh and/or 10-30 mesh.Once the necessary outer layer is formed on the core-shell, the waxcomponents (e.g. 1703, 1706, 1707, and 1709) and/or plug may be removedprior to or simultaneously with a firing process to sinter the materialsof the core-shell mold and/or the outer ceramic layer 1704; after which,any of the above-mentioned metals (e.g. superalloy) may be poured intothe mold.

As shown in FIGS. 25 and 26, once the outer ceramic layer 1704 isformed, the wax portions (e.g. 1703, 1706, 1707, and 1709) may beremoved through either melting and/or a chemical removal process.Further, as shown in FIG. 26, the plug 1718 may be removed throughsimilar and/or identical processes either before and/or after theremoval of the wax components 1703, 1706, 1707, and 1709. The plug 1718may also be removed simultaneously with the removal of any waxcomponents. The passages corresponding to the wax gate portions 1703,1706, 1707, 1709 form a cavity which may be in fluid communication withthe inner cavity 1711 of the core-shell mold. Further, once the plug isremoved, the ceramic layer 1704′ forms a cover/mold portioncorresponding to the opening 1712 and having an inner geometrycorresponding to the outer geometry of the previously placed plug 1718.

After the outer shell 1704 and 1704′ is formed, the cavity 1711 isfilled with metal (e.g. as shown by reference 1005 in FIGS. 13 and 14),such as a nickel based alloy, e.g., INCONEL®. Once the metal ishardened, the ceramic core and/or shell may be leached out. Uponleaching of the ceramic core-shell, the resulting cast component may bea turbine blade having a cooling hole pattern in the surface of theblade. It should be appreciated that although the figures provide across sectional view showing cooling holes at the leading and trailingedge of the turbine blade, that additional cooling holes may be providedwhere desired including on the sides of the turbine blades or any otherlocation desired. In particular, the present invention may be used toform cooling holes within the casting process in any particular design.In other words, one would be able to produce conventional cooling holesin any pattern where drilling was used previously to form the coolingholes. Further, as mentioned above, the ceramic shell portion 1704′provides a mold portion corresponding with the previously place plug1718 and allows for inspection and/or modification of the core-shellmold. The plug 1718, along with the abovementioned advantages allow fora portion of the ceramic core-shell mold to be removed and replaced bythe plug 1718. Further, the use of a plug 1718 may allow for a portionof the ceramic shell 1704′ to be thinner than the portion of thecore-shell mold having a shell and an outer shell 1704. Further theceramic shell portion 1704′ may be a material having differing thermalor structural qualities than the core-shell mold.

FIG. 27 shows a side view of an integrated core-shell mold according toanother embodiment of the present invention. As similarly to the otherabovementioned embodiments, and as shown in FIG. 27, the core 1800 maybe connected to the shell 1801 through several filaments 1802. The core1800 and the shell 1801 form a core-shell mold which defines a cavity1811 for investment casting a component, which in this example is aturbine blade. The core-shell mold may be connected to at least one waxcomponent, which may comprise at least one of a wax gate component. Thewax gate component may comprise a wax tube 1809, 1807, and/or a wax plug1808 and/or any selected portion of the final cast article. Thecore-shell mold may include a passageway 1806 in fluid communicationwith an inner cavity 1811 of the core-shell mold. The passageway 1806may have a wax component 1809, which may include a wax gate componentsuch as a tube, for example. A hole 1806 or a plurality of holes may beintegrated with a portion of the cavity 1811. Further, the core-shellmold may include an opening 1815, which may be in fluid communicationwith the cavity 1811. At any point during the abovementioned processes aceramic cover 1810 may be used to cover the opening 1815 prior tocoating the core-shell mold with an outer ceramic layer. The ceramiccover 1810 may be formed of a ceramic having the same or differentproperties than the core-shell mold. Further, the ceramic cover 1810 maybe formed using known 3-D printing and/or additive manufacturingprocess, including the abovementioned processes. The cover 1810 may havean inner surface that includes a specific desired geometry of the outersurface of the finished component, so that that once the ceramic coveris installed into the opening and is coated with the outer ceramiclayer, a specific mold geometry in the region previously defined by theopening 1815 is formed. The ceramic cover 1810 may also include engagingportions 1814 and 1812, to ensure the ceramic cover is correctly placedand oriented when the ceramic cover is installed in the opening 1815 andbefore the outer ceramic shell is formed on a surface of the plug. Forexample, engaging portions 1812 and 1814 may engage with engagementportions 1816 and 1817 on the core-shell mold as shown in FIG. 28. It isnoted that the abovementioned engaging and engagement portions are notlimited to the structure shown; for example, the engaging portions maybe provided so as to engage with an engagement portion provided on thecore portion 1800 of the core-shell mold.

The opening 1816 may be used for inspection and/or may include a portionof the mold that is desirable to have altered or changed in themanufacturing process. For example, it may be desirable to form a firstturbine blade having a first outer geometry and a second turbine bladehaving a second outer geometry while using the same core-shell mold. Thefirst and/or second external geometries may be formed by installing afirst ceramic cover having a first geometry into the opening 1816 of afirst core-shell mold and installing a second ceramic cover having asecond geometry into the opening 1816 of a second core-shell mold,wherein the first and second core-shell molds have substantiallyidentical geometries. The ceramic cover 1810 may also be altered basedon a desired change or alteration in geometry without having to alter orform a new ceramic core-shell mold.

As shown in FIG. 28, the core-shell mold may be formed and any optionalwax component (e.g. 1806, 1807, and 1809) may be connected, and theceramic cover 1810 may be installed into opening 1815 of the core-shellmold prior to forming the outer ceramic layer. As shown in FIG. 29, anouter ceramic layer 1804 may then be formed on the outer surface 1801 ofthe core-shell mold, the ceramic cover 1810, and any wax component (e.g.1806, 1807, and 1809). The outer ceramic layer 1804 may be formedthrough dipping of the core-shell mold into a ceramic slurry. The outerceramic layer 1804 may further be formed as a single and/or multi-layersubstrate formed through the dipping of the core-shell mold, the ceramiccover, and/or the gate portions into a ceramic slurry, drying theslurry, and dipping the core-shell mold into a either the same ceramicslurry and/or different type of slurry to form an outer shell on thecore-shell mold. Further, a refractory grain may be sifted onto theslurry coating between layers. It is noted that other forms of forming aceramic coating could be used in lieu of or in combination with thedipping process mentioned above. For example, a ceramic and/or othermaterial may be sprayed onto the core-shell.

As an example, the above-mentioned slurry may include any of theabove-mentioned materials or materials known in the art; for example:colloidal silica and a ceramic powder (e.g. Al2O3, SiO2, ZrSiO4, ZrO2,Y2O3, AIN, SiC). The above-mentioned grain may be applied between layersand may include ceramic sand (e.g. Al2O3, SiO2, ZrSiO4, ZrO2, Y2O3, AIN,SiC) in a mesh of 90-120. Subsequent layers of slurry may be applied andsubsequent layers of ceramic sand may be applied in 20-70 mesh and/or10-30 mesh. Once the necessary outer layer is formed on the core-shellmold, the ceramic cover, the wax components (e.g. 1806, 1807, and 1809),the wax components may be removed prior to or simultaneously with afiring process to sinter the materials of the core-shell mold, theceramic cover 1810, and/or the outer ceramic layer 1804; after which,any of the above-mentioned metals (e.g. superalloy) may be poured intothe mold.

Once the outer ceramic layer 1804 is formed, the wax portions (e.g.1806, 1807, and 1809) may be removed through either melting and/or achemical removal process. Once the wax portions are removed, passagescorresponding to the wax portions 1803, 1806, 1807, 1809 form a cavitywhich may be in fluid communication with the inner cavity 1811 of thecore-shell mold. Further, once the outer ceramic layer 1804 is formed,the ceramic door 1810 becomes portion of the mold having an innergeometry corresponding to the desired outer geometry of the component.

After the outer shell 1804 is formed, the cavity 1811 is filled withmetal (e.g. as shown by reference 1005 in FIGS. 13 and 14), such as anickel based alloy, e.g., INCONEL®. Once the metal is hardened, theceramic core and/or shell may be leached out. Upon leaching of theceramic core-shell, the resulting cast component may be a turbine bladehaving a cooling hole pattern in the surface of the blade. It should beappreciated that although the figures provide a cross sectional viewshowing cooling holes at the leading and trailing edge of the turbineblade, that additional cooling holes may be provided where desiredincluding on the sides of the turbine blades or any other locationdesired. In particular, the present invention may be used to formcooling holes within the casting process in any particular design. Inother words, one would be able to produce conventional cooling holes inany pattern where drilling was used previously to form the coolingholes. Further, as mentioned above, the ceramic shell portion 1804 andceramic cover 1810 provides a mold portion corresponding with theinstalled ceramic cover 1810. As mentioned above, the ceramic cover 1810may be used to allow for inspection and/or modification of thecore-shell mold. The ceramic cover 1810, along with the abovementionedadvantages allows for a portion of the ceramic core-shell mold to beremoved and replaced by ceramic cover 1810. Further, the use of theceramic cover 1810 may allow for a portion of the ceramic shell 1804 tobe thinner than the portion of the core-shell mold having a shell and anouter shell 1804. Further the ceramic cover 1810 may be formed amaterial having differing thermal or structural qualities than thecore-shell mold and the outer ceramic shell 1804.

In an aspect, the present invention relates to the core-shell moldstructures of the present invention incorporated or combined withfeatures of other core-shell molds produced in a similar manner. Thefollowing patent applications include disclosure of these variousaspects and their use:

U.S. patent application Ser. No. 15/377,728, titled “INTEGRATED CASTINGCORE-SHELL STRUCTURE” with attorney docket number 037216.00036/284976,and filed Dec. 13, 2016;

U.S. patent application Ser. No. 15/377,711, titled “INTEGRATED CASTINGCORE-SHELL STRUCTURE WITH FLOATING TIP PLENUM” with attorney docketnumber 037216.00037/284997, and filed Dec. 13, 2016;

U.S. patent application Ser. No. 15/377,796, titled “MULTI-PIECEINTEGRATED CORE-SHELL STRUCTURE FOR MAKING CAST COMPONENT” with attorneydocket number 037216.00033/284909, and filed Dec. 13, 2016;

U.S. patent application Ser. No. 15/377,746, titled “MULTI-PIECEINTEGRATED CORE-SHELL STRUCTURE WITH STANDOFF AND/OR BUMPER FOR MAKINGCAST COMPONENT” with attorney docket number 037216.00042/284909A, andfiled Dec. 13, 2016;

U.S. patent application Ser. No. 15/377,673, titled “INTEGRATED CASTINGCORE SHELL STRUCTURE WITH PRINTED TUBES FOR MAKING CAST COMPONENT” withattorney docket number 037216.00032/284917, and filed Dec. 13, 2016;

U.S. patent application Ser. No. 15/377,787, titled “INTEGRATED CASTINGCORE SHELL STRUCTURE FOR MAKING CAST COMPONENT WITH NON-LINEAR HOLES”with attorney docket number 037216.00041/285064, and filed Dec. 13,2016;

U.S. patent application Ser. No. 15/377,783, titled “INTEGRATED CASTINGCORE SHELL STRUCTURE FOR MAKING CAST COMPONENT WITH COOLING HOLES ININACCESSIBLE LOCATIONS” with attorney docket number037216.00055/285064A, and filed Dec. 13, 2016;

U.S. patent application Ser. No. 15/377,766, titled “INTEGRATED CASTINGCORE SHELL STRUCTURE FOR MAKING CAST COMPONENT HAVING THIN ROOTCOMPONENTS” with attorney docket number 037216.00053/285064B, and filedDec. 13, 2016.

The disclosures of each of these applications are incorporated herein intheir entirety to the extent they disclose additional aspects ofcore-shell molds and methods of making that can be used in conjunctionwith the core-shell molds disclosed herein.

This written description uses examples to disclose the invention,including the preferred embodiments, and also to enable any personskilled in the art to practice the invention, including making and usingany devices or systems and performing any incorporated methods. Thepatentable scope of the invention is defined by the claims, and mayinclude other examples that occur to those skilled in the art. Suchother examples are intended to be within the scope of the claims if theyhave structural elements that do not differ from the literal language ofthe claims, or if they include equivalent structural elements withinsubstantial differences from the literal language of the claims.Aspects from the various embodiments described, as well as other knownequivalents for each such aspect, can be mixed and matched by one ofordinary skill in the art to construct additional embodiments andtechniques in accordance with principles of this application.

1. A method of fabricating a ceramic casting mold comprising the stepsof: (a) connecting at least one wax component to a ceramic core-shellmold, the ceramic core-shell mold comprising at least: a first coreportion; a first shell portion; and a second shell portion, wherein thefirst shell portion is adapted to interface with at least the secondshell portion to form at least a portion of a first cavity between thecore portion and the first and second shell portions; (b) applying asecond ceramic material to coat at least a portion of the ceramiccore-shell mold and the wax component with the second ceramic material;and (c) removing the wax component to form at least a second cavity influid communication with the first cavity.
 2. The method for fabricatinga ceramic casting mold of claim 1, wherein the core-shell mold is formedby: (i) contacting a cured portion of a workpiece with a liquid ceramicphotopolymer; (ii) irradiating a portion of the liquid ceramicphotopolymer adjacent to the cured portion through a window contactingthe liquid ceramic photopolymer; (iii) removing the workpiece from theuncured liquid ceramic photopolymer; and (iv) repeating steps (i)-(iii)until the core-shell ceramic mold is formed of a first ceramic material.3. The method of fabricating a ceramic casting mold of claim 1, whereinthe wax component comprises a plurality of wax gate components.
 4. Themethod of fabricating a ceramic casting mold of claim 3, wherein each ofthe first shell portion and second shell portion portions is connectedto a wax gate component.
 5. The method of fabricating a ceramic castingmold of claim 1, wherein at least one of the shell portion of thecore-shell mold comprises at least one opening in fluid communicationwith the first cavity, wherein the wax component is connected to theopening.
 6. The method of fabricating a ceramic casting mold of claim 1,wherein the second ceramic material is coated on portion of thecore-shell ceramic mold and wax component by dipping the core-shellceramic mold and wax component into a ceramic slurry.
 7. The method offabricating a ceramic casting mold of claim 1, wherein the core-shellportion is formed of a first ceramic material having a differentsolubility, heat transfer coefficient, or porosity than said secondceramic material. 8.-16. (canceled)
 17. A method of preparing a castcomponent comprising steps of: (a) assembling a first ceramic coreportion and a first ceramic shell portion of a two piece ceramic moldwith at least a second ceramic shell portion to form a two piece ceramicmold comprising a first cavity between the first ceramic core portionsand the first and second ceramic shell portions, wherein the firstcavity is adapted to define the shape of the cast component upon castingand removal of the two piece ceramic mold; (b) connecting a waxcomponent to at least one of the first ceramic shell portion and secondceramic shell portion; (c) at least partially covering the waxcomponent, and first and second ceramic shell portion with a thirdceramic shell portion; (d) removing the wax component to form a secondcavity in fluid communication with the first cavity.
 18. The method ofpreparing a cast component of claim 17 further comprising steps of:providing a liquid metal into the first cavity of the two piece ceramiccasting mold through the second cavity and solidifying the liquid metalto form the cast component; and removing the third ceramic shell portionand two piece ceramic casting mold from the cast component.
 19. Themethod of preparing a cast component of claim 18, wherein the waxcomponent is removed prior to providing liquid metal into the firstcavity of the casting mold.
 20. The method of preparing a cast componentof claim 17, wherein the wax component comprises a plurality of wax gatecomponents.
 21. The method for fabricating a ceramic casting mold ofclaim 1, wherein the ceramic core-shell mold further comprises aplurality of filaments joining the first core portion and the firstshell portion, wherein each of the plurality of filaments is monolithicwith the first core portion and the first shell portion and spansbetween the first core portion and the first shell portion, theplurality of filaments adapted to define a plurality of holes providingfluid communication between the first cavity within the cast componentdefined by the first core portion and an outer surface of a castcomponent upon removal of the ceramic casting mold.
 22. The method forfabricating a ceramic casting mold of claim 21, wherein the core-shellmold is formed by: (i) contacting a cured portion of a workpiece with aliquid ceramic photopolymer; (ii) irradiating a portion of the liquidceramic photopolymer adjacent to the cured portion through a windowcontacting the liquid ceramic photopolymer; (iii) removing the workpiecefrom the uncured liquid ceramic photopolymer; and (iv) repeating steps(i)-(iii) until the core-shell ceramic mold is formed of a first ceramicmaterial.
 23. The method of fabricating a ceramic casting mold of claim21, wherein the wax component comprises a plurality of wax gatecomponents.
 24. The method of fabricating a ceramic casting mold ofclaim 23, wherein each of the first shell portion and second shellportion portions is connected to a wax gate component.
 25. The method offabricating a ceramic casting mold of claim 21, wherein at least one ofthe shell portion of the core-shell mold comprises at least one openingin fluid communication with the first cavity, wherein the wax componentis connected to the opening.
 26. The method of fabricating a ceramiccasting mold of claim 21, wherein the second ceramic material is coatedon portion of the core-shell ceramic mold and wax component by dippingthe core-shell ceramic mold and wax component into a ceramic slurry. 27.The method of fabricating a ceramic casting mold of claim 21, whereinthe core-shell portion is formed of a first ceramic material having adifferent solubility, heat transfer coefficient, or porosity than saidsecond ceramic material.